I just got a Harman / Kardon AVR520 receiver rated at 75 watts / channel. After hooking up my M80ti's and listening for a bit (awesome!) the receiver starts shutting down by putting itself into standby mode. The only possible explanation I can come up with is impedence problems, covered on the Harman / Kardon website:

"All Harman Kardon Audio/Video receivers can handle most 4 and 6 ohm speakers on the market today. However, there are some manufacturers' speakers that have a minimum impedance well below the 4 and 6 ohm nominal impedance. In this situation, the receiver will protect itself by going into standby mode. This will not damage the speakers or the electronics, but it is an indication that the speaker in question is not compatible with our receiver. Note: The continued use of the receiver with speakers that cause it to shut down can result in eventual failure of the receiver which is not covered by the warranty."

Is this what is going on here? I know the M80ti's are rated at 4 Ohms but I can find no other reason for this to happen. I know these speakers would probably love a separate amp, but this is a pretty beefy receiver and I wont be pleased if it is not sufficient, since I wasn't planning on buying any more equipment at present.

There has been some discussion on this at the Hometheaterforum web site. It seems that many H/K owners are tracing this shut-down problem to the H/K's finiky power supply. Apparently, H/K receivers can't handle an over unruly power coming from the wall. Appartments are the worst, but it can also happen in a single family house if you have too much on that curcit or if you have your drier, microwave, and blender goning at the same time can cause a power draw and give you noisy power in the entire house. It might be worth trying out a power conditioner or a current stablizer.

You make a good point here. While I have never heard of this being a problem with the HK units (but then again not having a HK I wouldn't be paying attention to this) If the HK has a finiky PS then certainly dirty power will play havoc with the unit. There are a number of good clean power sources available at reasonable prices so it may be worth trying. I have a unit on my system and I swear it improved the sound, not drastically and maybe it is even a phycological difference. I have not done any blind tests, and I wanted to add some power surge protection/filtering to protect my investment anyway. These units can't hurt your system and clean power should only make it better.

"Before you go any further, have you tried hooking up to a different set of speakers to see if there is a problem in the receiver itself?"

Thanks for the reply - actually to be honest I don't have any other speakers. Before buying this receiver and the Epic 80 set I was just using my computer for music. I can borrow some small speakers however and test this out.

"It might be worth trying out a power conditioner or a current stablizer."

Thanks for the suggestion; will a computer UPS work for testing purposes? Or would I need something specifically for audio equipment? Right now I have a Monster Cable power strip which supposedly provides "clean power", but it has no internal battery so I can't see how it could help if the receiver and other equipment is drawing too much current.

I have a computer UPS and am quite familiar with those - not familiar with solutions specific to audio equipment.

The Monster Cable power strip much like (although to a lesser extent) the larger units from Monster Cable and several other manufactures provide a source of filtered power, it does not provide any source of stable power. Using a UPS make much difference at this point. You could try it, but if you are already using one of these strips then I suspect that dirty power is not your problem. Even the most basic stage 1 or stage 2 filtering should clean up the power more then enough to rule that out. Look up your model on the Monster Cable web site www.monstercable.com to see what it's specs are. Make sure that it does have filtering and not just surge suppression. Have you tried other speakers? Does the problem still exist or is it gone when you change speakers. It maybe also that the problem only shows up when driving speakers with 4-6 ohm loads. You will need to check this out, if the unit is still new you may want to take it back and have them exchange it for another to test out.

Hi Doug,
I've sold lots of AVR520 with the M80TiSe with no problems yet. The AVR520 has a very robust power supply. The M80TiSe is an 'easy' four ohm load too.
I would suggest checking your speakerwire connections for short circuits at the speaker and amp ends. If one strand of wire is touching the opposite, the '520 will tolerate that at very low levels but as soon as you turn it up, then the protection circuit kicks in. Hopefully you find that's all it is and no servicing is required.

Thanks Marc - actually I am using Monster Cable Z1's for the M80Ti's and these have plugs with no exposed wires as I'm sure you're aware. I've looked at the back of the AVR520 and speakers to make sure everything is OK and not reversed and it's fine. Also, I've now tried connecting this to a TrippLite UPS computer battery backup and the same problems occur. Turn it up past -16 give or take and it will go into standby after a few seconds up to a few minutes. Should I be calling Harmon / Kardon now?

Hi John - I did indeed try a beefy TrippLite computer UPS on the battery jack which provides constant filtered power and had the same problem. My Monster Power strip is the HTS850. It does indeed have clean power as a feature, "Stage 1 Clean Power." I guess since the AVR520 has been going into standby while connected even to a UPS we're dealing with something else here.

As far as testing other speakers goes, the only ones I have now would likely be blown if I crank the AVR520 up to the point where it cuts out. Marc has sold this particular setup though and apparently he hasn't seen this unit have any trouble with the M80Ti's.

Is there anything else you (or any other forum members) suggest I might try or should I assume I have a bad receiver?